Photolithography mask repair

ABSTRACT

Masks can be repaired by creating a structure that is different from the original design, but that produces the same aerial image. For example, missing opaque material can be replaced by implanting gallium atoms to reduce transmission and quartz can be etched to an appropriate depth to produce the proper phase. In another aspect, a laser or other means can be used to remove an area of a mask around a defect, and then mask structures, either the intended design structures or alternate structures that produce the same aerial image, can be constructed using charged particle beam deposition and etching. For example, an electron beam can be used to deposit quartz to alter the phase of transmitted light. An electron beam can also be used with a gas to etch quartz to remove a layer including implanted gallium atoms. Gallium staining can also be reduced or eliminated by providing a sacrificial layer that can be removed, along with the implanted gallium atoms, using, for example, a broad ion beam. In another aspect, a charged particle beam can be programmed to etch a defect using three-dimensional information derived from two charged particle beams images of the defect from different angle.

[0001] This application claims priority from U.S. Provisional Pat. App.No. 60/411,699, filed Sep. 18, 2002, which is hereby incorporate byreference.

TECHNICAL FIELD OF THE INVENTION

[0002] The present invention relates to the field of charged particlebeam tools for forming, altering and viewing microscopic structures, inparticular to repair of photolithography masks.

BACKGROUND OF THE INVENTION

[0003] Photolithography is a process that is used to create smallstructures, such as integrated circuits and micromachines. Thephotolithography process entails exposing a radiation-sensitivesubstance, called photoresist, to a pattern of light or other radiation.The pattern is typically created by passing the radiation through amask, which is composed of a substrate with a pattern on its surface.The pattern blocks some of the radiation or changes its phase to createexposed and unexposed areas on the radiation-sensitive material. In abinary intensity mask, the pattern is made of a light absorbing materialon an otherwise transparent substrate. In a phase shift mask (“PSM”),the pattern consists of material that shifts the phase of the lightpassing though it to create an interference on the photoresist thatproduces a sharp image. The image produced on the photoresist isreferred to as the “aerial image” of the mask. The size of the structurethat can be produced is limited by the wavelength of radiation used;shorter wavelengths can produce smaller structures.

[0004] As photolithography processes are called upon to produceever-smaller structures, lithography systems are being developed thatuse smaller wavelengths of radiation, including infra-red and even x-rayradiation. (The terms “light” and “photolithography” are used in ageneral sense to also include radiation other than visible light.)Systems are now being developed that can produce structures havingdimensions of 70 nm and smaller. Such structures can be fabricated byphotolithography using light having a wavelength of 193 nm or 157 nm.Some photolithography masks used with such short wavelengths use areflective, rather than a transmissive, pattern on the mask because thesubstrate is not sufficiently transparent to such small wavelengths ofradiation. In such masks, radiation is reflected from the mask onto thephotoresist.

[0005] The photolithography mask must be free of manufacturingimperfections if the mask is to accurately produce the desired exposurepattern. Most newly fabricated masks have defects such as missing orexcess pattern material and, before such masks can be used, the defectsare repaired, often by using a charged particle beam system to remove ordeposit material onto the mask substrate.

[0006] The requirement for smaller wafer features in photolithographyplaces ever-increasing demands upon the three-dimensional structuringcapabilities of the techniques used to repair defects on the photomasks.Repair strategies for clear defects on chrome binary-intensity-masks(BIM) and molybdenum-silicide attenuated-phase-shift-masks (MoSi PSM)are typically based upon reconstructing as closely as possible theoriginal physical structure of the mask feature along with the opticalproperties of the materials. While direct replacement, i.e., thesubstitution of a void with the original mask material, is the moststraightforward approach to clear defect repair, a number of practicalconsiderations greatly limit the optical fidelity of this repairstrategy. For example, the patching of clear defects, that is, missingabsorber or phase shifting material, on both BIM and PSM by focused ionbeam (FIB) induced deposition typically does not employ the nativemasking material but rather a carbon-based material whose height isadjusted to mimic the desired optical properties. In the case of MoSiPSM, the deposited height can satisfy only one of the designed valuesfor phase and transmission; in practice the latter is matched due to theease of measurement although the former is more important for sharpeningthe edge transition. Furthermore, the fabrication of a structure byFIB-induced deposition of material from a gas phase onto the surface isa complicated process, which is very difficult to control on thenanometer scale.

[0007] In the case of an opaque defect, that is, the presence of extraabsorber or phase shift material, the defect can be repaired by removingthe extra material using charged particle beam, for example, a focusedbeam of gallium ions. Unfortunately, the ion beam also damages the masksurface and implants ions into the substrate, which adversely affectsthe transmission of light through the substrate. As shorter wavelengthsare used in photolithography, imperfections in the substrate have agreater effect on the aerial image of the mask. Any alteration of thesubstrate caused by the repair affects the mask performance, so new maskrepair systems are needed that will reduce the effect on the substrate.

[0008] One method of reducing the effects of ion beam mask repairentails scanning a charged particle beam across the repaired area in thepresence of an etchant gas, such as xenon-difluoride. Such a process isdescribed, for example, in U.S. Pat. No. 6,042,738 to Casey, Jr. et al.The clean-up step described in U.S. Pat. No. 6,042,738 adds an extrastep to the mask repair process, and the results may still not becomparable to an area that was originally produced without defect. Thus,a method is needed to correct a defective mask so that it projects thedesired image onto a work piece.

[0009] Therefore, even after a defect is repaired, the repaired area maystill have characteristics that are different those of an area that wasoriginally defect-free. For example,

SUMMARY OF THE INVENTION

[0010] An object of the invention is to provide a system for repairingphotolithography masks.

[0011] The inventive system includes several aspects that facilitate theuse of a charged particle beam system for mask repair. In accordancewith one aspect of the invention, applicants recognized that just as theoptical function of a given mask feature, that is, its aerial image, maybe achieved by a wide variety of physical structures including thoseemployed in binary intensity, attenuated phase-shift, and alternatingaperture phase-shift mask technologies, similarly, the freedom to designa given optical functionality through different means is also availablefor the repair of a defect on a photomask feature.

[0012] Diverse structures and structuring techniques can be applied tothe defect area in order to reproduce the desired aerial image of thefeature without necessarily having to recreate the intended structure ofthe mask feature. In one embodiment of the invention, this freedom isexploited in order to compensate for a missing piece of masking materialon BIMs and PSMs. That is, rather than trying to recreate the mask as itwas designed, applicants produce an alternative structure that usesimplanted ions and that prints the nearly the same circuit feature asthe original design. Thus, the effects of scanning a charged particlebeam over the mask, which effects are typically unintentional anddeleterious, are utilized to effect intended changes in the substrate.

[0013] In accordance with other aspects of the invention, multiple stepscan be used to repair a defect, including steps involving combinationsof ion beam, electron beam, and laser processing. For example, stainsfrom ion implantation can be used as part of the repair, can be removedby an electron beam, or can be removed along with a sacrificial layer.In some repairs, an electron beam can be used in place of an ion beam toeliminate staining. In some repairs, a laser can be used to remove adefective area and then the area can be reconstructed using particlebeam deposition.

[0014] The foregoing has outlined rather broadly some of the featuresand technical advantages of various aspects of a preferred system of thepresent invention in order that the detailed description of theinvention that follows may be better understood. Additional features andadvantages of the invention will be described hereinafter. It should beappreciated by those skilled in the art that the conception and specificembodiment disclosed herein may be readily utilized as a basis formodifying or designing other structures for carrying out the samepurposes of the present invention. It should also be realized by thoseskilled in the art that such equivalent constructions do not depart fromthe spirit and scope of the invention as set forth in the appendedclaims. It should also be realized that while a preferred system forrepairing photomasks may implement many of the inventive aspectsdescribed below, many of the inventive aspects can be appliedindependently, or in any combination, depending upon the goals of aspecific implementation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] For a more thorough understanding of the present invention, andthe advantages thereof, reference is now made to the followingdescriptions taken in conjunction with the accompanying drawings, inwhich:

[0016]FIG. 1 is a flowchart showing the steps of one preferredembodiment of the invention

[0017]FIG. 2 shows a clear defect and its repair.

[0018]FIG. 3 shows a dual beam system that could be used to repair amask in accordance with the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Applicant recognized that the important end product of a maskrepair is not that the original mask is reconstructed, but that theimage of the repaired mask projected onto the wafer is as close aspossible to the intended image. By using software that calculates theaerial image of a three-dimensional structure on a photomask, applicantsare able to prediction of the optical effects of the artifacts whichaccompany the FIB repair of defects. As a result, a repair can bedesigned that may not reproduce the intended design structure, but thatproduces an aerial image that will produce substantially the sameresult. For example, the light blocking characteristics of galliumstaining can be used in the context of a method for defect repair,particularly for repair of clear defects. Basically the galliumimplanted during scanning, at certain doses, is sufficient to reducetransmission or reflectivity, akin to material depositions. Anotherexample, which is known in the art, is to repair missing phase shiftmaterial by reducing the thickness of the substrate at the defect area,rather than depositing additional phase shift material. The thinned areaalso shifts the phase of the transmitted light relative to unpatternedsubstrate.

[0020] Repair strategies are preferably based upon the application ofnanostructuring methods with high resolution and repeatability. Also,the repair strategy should preferably be such that the aerial image ofthe repaired area is preferably tolerant to variations in the physicaldimensions and optical properties of the repaired feature. Thus, ratherthan attempting to reconstruct the original structure of the defectivearea, one can chose a repair technique that has the properties justdescribed and that produces a structure that, while it may be physicallydifferent from the intended structure, has a similar aerial image.

[0021]FIG. 1 shows a flow chart listing steps of a preferred embodimentof the present invention. In step 102, a defect is identified andcharacterized. Defects are typically located using a mask inspectiontool such as those available from KLA-Tencor Corporation, San Jose,Calif., and then characterized, for example, using a scanning electronmicroscope or a scanning probe microscope. The data required tocharacterize a defect for repair depend upon the type of defect and caninclude, for example, location, size, and topology, that is, itsthree-dimensional shape. In step 104, the intended aerial image, thatis, the projected light from a defect-free mask, for the area adjacentthe defect is determined, for example, by using the SOLID-CM programfrom SIGMA-C GmbH, Munich, Germany. In step 106, a repair strategy isdetermined that will produce approximately the same aerial image as adefect-free mask. The repair strategy preferably produced a repairedmask that has high transmission at the desired exposure wavelength, anda deviation from the intended feature size, when printed under apredetermined set of stepper and resist parameters, of less than orequal to plus or minus about ten percent. The repair strategy ispreferably one that produces a result close to the original mask andthat is relatively simple to implement and repeatable. In step 108, therepair is performed. An example of a repair strategy is described below.

[0022] An example of a repair strategy that does not recreate theoriginal structure is the use of implanted gallium atoms to correctmissing absorber material. The use of FIB milling in conjunction withgallium staining provides a substantial improvement over the prior artcarbon deposition repair process in resolution, repeatability, andtolerance to variations in the physical dimensions and opticalproperties of the repaired feature. In conjunction with mask simulation,the inventive system uses the optical functionality of an unavoidablebyproduct of the repair process, to turn the artifact into an asset. Byincorporating mask simulation into the repair process, the repair toolcan more effectively produce a repaired mask that has properties moresimilar to the original.

[0023] While implantation is an unavoidable consequence of FIBprocesses, its effects upon the repair of mask defects were previouslyeither ignored or minimized. With the reduction in the wavelength oflight used in optical lithography to DUV, the reduction in lighttransmission attendant with gallium implantation becomes a dominantartifact of the repair process for opaque defects. At a free-spacewavelength of 193 nm, a relative transmission of only twenty threepercent is experimentally measured for a “saturated” gallium stain, inwhich an equilibrium has been established between the concurrent effectsof the implantation of the ion source species and the removal of thestained quartz substrate by ion-induced sputtering. Rather than treatinggallium staining as a detrimental effect that is to be minimized oreliminated, applicants make use of the change in characteristics of themask due to gallium implanting to repair the mask. This aspect of theinvention is referred to as the “functionalization” of the gallium stainfor the repair of clear defects.

[0024] Ion implantation is a simple, reproducible, and fast FIB-basedrepair process that can accurately produce a pattern at a highresolution. The functionalization of the implantation staining for thepatching of clear defects can provide a number of advantages.Functionalization of the gallium stain enhances the quality of therepair of clear defects on binary intensity and attenuated phase-shiftphotomasks, in part because the repair process is relatively simple andis more tolerant of system errors and also because the invention canpredictably vary the phase characteristics of the repaired area at afixed transmission.

[0025] In some embodiments, metallic atoms are implanted into thetransparent substrate by a focused beam of ionized metal atoms to repairclear defects on binary intensity masks. Saturated stains, in which anequilibrium is reached in the composition of the sputtered surface, arereadily achieved with current FIB repair tools and provide a controlledand reproducible method for fabricating a fixed transmission loss overan arbitrary area. Phase effects due to the use of non-opaque materialfor the masking layer and due to the etching of the quartz substratewhich occurs prior to the establishment of a saturated stain arecontrolled by varying the depth etched into the quartz. Thus, therepaired area can produce not only the transmission, but also the phase,of the original mask design. The phase effects are used not only in therepair of phase shift masks, but to produce the desired aerial image inbinary masks.

[0026] As another example, the invention can be used to repair cleardefects on an attenuated phase shift masks. Saturated stains provide amore controlled and reproducible method for the precise definition of afixed transmission loss over an arbitrary area than the current carbonpatch process. Furthermore, phase effects can be independentlycontrolled by varying the depth etched into the quartz. For example, onemight etch a step into quartz to mimic the desired phase, and thensubsequently deposit a material of the desired thickness to provide theintended transmission.

[0027]FIG. 2 illustrates a simple repair designed to use a gallium stainto fix a clear defect in a binary mask 200. Mask 200 includes chromiumlines 202 spaced 400 nm apart, and one line 202 is missing chromiumabsorber in a triangular defect region 204. Clear defect region 204extends about 400 nm along the edge of chromium line 202 intrudes about200 nm into chromium line 202. In accordance with an embodiment of theinvention, the defect is repaired by filling the triangular defect area204, along with a rectangular area 206 that extends 80 nm into thequartz space, with a saturated Ga stain, that comprises gallium atomsfrom a gallium liquid metal ion beam implanted into the quartz to depthof about 24 nm. In other words, rather than filling clear defect area204 with an opaque material such as carbon, gallium is implanted intothe clear defect area and into an adjacent area extending past theoriginally intended edge of the chromium line. The resulting aerialimage of the mask than approximates the aerial image of a mask thatmanufactured without the defect.

[0028] For the repair described above, the transmission values that arepredicted by the version 2.7.0 of the SOLID-CM topographic masksimulator at specific locations in this repair are shown in Table 1:TABLE 1 Transmission For Ga-Stained Repair Process Transmission at theunder Cr under Cr middle of line with line next Qz space defect todefect Original Defect 119.8% 134.8% 101.9% With Ga Stain 97.6% 106.2%96.9%

[0029] Because light is diffracted, that is, bent around the edge of thechrome lines, light is detected in areas under the chrome lines and nearthe edges of the chrome lines. TABLE 1 shows that the transmission issignificantly reduced by the gallium staining. In the table of FIG. 1,100% represents the light that would be transmitted at a location ifthere were not missing absorber material. The high transmission values,that is, greater than 100%, are due to missing chrome, which would‘block’ the light. The transmission is restored to closer to thedesirable 100% by blocking some light with the nontransparent galliumimbedded in the quartz. The extension of the stain outside the originaldefect area into the surrounding quartz compensates for the partiallytransparency in the area of the missing chromium and substantiallyimproves the optical fidelity of the repaired feature. The thickness issomewhat reduced by etching during implantation.

[0030] For attenuated phase-shift masks, the depth of the etched regionwith the saturated gallium stain is adjusted in order to produce thedesired phase shift relative to the unetched and unstained quartz. As inbinary masks, the discrepancy between the desired transmission and theactual saturated stain transmission is compensated for by adjusting theboundaries of the repair area.

[0031] The repair can be performed using the same focused ion beamsystem scanning parameters, i.e., pixel spacing/timing and chargeneutralization scheme, during the repair that are used in imaging. Withthis embodiment, there is no halo, that is, no unintentional depositionin the outskirts of the beam, which causes undesirable transmission lossor flood gun stain to cleanup or to compensate for. As in the repair ofopaque defects, edge biases, that is, placement of the edge of therepair offset from the edge of the feature, should be selectivelyadjusted to improve transmission. Typically this means deliberatelyoveretching about 30 nm into a chrome line. This repair strategy hasgreater tolerance for edge-placement error than does a deposition of anopaque material, because of the partial transparency of the stain.

[0032] The invention is particularly useful for, although not limitedto, repairing lithography masks used for the 70 nm lithography node andbeyond, including optical, x-ray, extreme ultra violet (EUV), differentabsorbers, and phase shift masks technologies.

[0033]FIG. 3 shows schematically a dual beam system 300 that is usefulfor implementing the invention. System 300 includes an ion beam column302 and an electron beam column 304. The two beams impinge a work piece306 at points 308 and 310 respectively, points 308 and 310 being aknown, small distance apart, so that a point on the work piece can bereadily shifted to use the appropriate beam. Such a system is described,for example, in U.S. Provisional Pat. App. No. 60/487,792, filed Jul.14, 2003 for a “Dual Beam System.” A charge neutralization device, suchas a flood gun or an ion generator, can be used to neutralize chargeaccumulated on the mask. The stage that supports the work piecepreferably has nanometer repeatability to allow for imaging with theSEM, and repositioning under FIB to ensure edge placement error lessthan 7 nm at three standard deviations. Edge placement, that is,determining the relative position of the edge of the repaired areacompared to the edge of the feature above or below the repair, can bedetermined using an optical laser, or preferably using ion beam imaging,which applicants have shown to be more accurate for edge placement thanlaser methods.

[0034] In other embodiments, the columns are arranged such that thebeams are parallel, as described in U.S. Prov. Pat. App. 60/411,699,filed Sep. 18, 2002, and uses an ion generator for chargeneutralization. One column is preferably tilted or tiltable with respectto the other column to provide three-dimensional topographicalinformation for phase shift mask repair.

[0035] Focused ion beam column 302 includes an ion source 308,preferably a gallium liquid metal ion source (LMIS). Other ion sourcesthat could be used include a silicon/gold eutectic LMIS and a plasma ionsource, depending upon the repair strategy. By using a mask simulationprogram as described above, skilled persons would be able to determinethe effects of the implantation of materials other than gallium and usethose effect to effect repair of defects. The column can use a focusedbeam or a shaped beam. The invention is not limited to any particulartype of charged particle beam column.

[0036] Mask repair can use both electron beam and ion beam etching anddeposition. In embodiments in which it is not desired to use ionimplantation staining, an electron beam repair is preferred because iteliminates ion implantation. For example, MoSi and TaN₂ absorbermaterial can be etched using an electron beam and an etchant gas, suchas XeF₂, as described in U.S. patent application Ser. No. 10/206,843 for“Electron Beam Processing,” by Musil et al., which is herebyincorporated by reference. The gallium beam can be also be used foretching chrome, and the gallium-implanted layer can be removed using thegas assisted etching using the ion beam or an electron beam.

[0037] Using a tilted beam can provide three-dimensional informationabout the work piece. Three-dimensional information is useful, forexample, in the repair of quartz bumps defects on a phase shift mask.Such defects, being made of the same material as the substrate, do notexhibit much contrast with the substrate in an image, and so can bedifficult to repair without damaging the substrate. U.S. patentapplication Ser. No. 10/636,309, filed Aug. 7, 2003, for “RepairingDefects On Photomasks Using A Charged Particle Beam And TopographicalData From A Scanning Probe Microscope,” describes a method of usingthree-dimensional topographical information to repair defects in phaseshift masks. A tilted charged particle beam can be used to provide athree-dimensional image instead of the Scanning Probe Microscopedescribed in U.S. patent application Ser. No. 10/636,309. If a chargedparticle beam system provides the three-dimensional data, it becomesunnecessary to remove the work piece from the vacuum chamber to obtainthe information, thereby improving productivity.

[0038] A strategy to repair a particular defect can include multiplestages, using combinations of ion, electron or lasers. For example, anion beam can be used to remove an opaque defect and then an electronbeam can be used to etch a layer of gallium-implanted quartz using XeF₂as post processing to restore transmission.

[0039] In another repair strategy, an electron beam can be used torepair missing quartz on PSM masks. For example, when an electron beamis scanned over the defect in the presence of a precursor gas, such asTEOS or TMCTS, the precursor gas will decompose under the influence ofthe electron beam to deposit quartz to replace the missing quartz of themask. In some embodiments, one can also supply an oxygen-containingmaterial, such as water, oxygen, or hydrogen peroxide, to supplyadditional oxygen to assist in the quartz deposition. The depositedstructures can be used to simultaneously match phase and transmission ofthe mask.

[0040] In another repair strategy, a sacrificial layer of quartz can beglobally or selectively added to the mask substrate during itsmanufacture. After all necessary mask repairs are performed, thesacrificial layer can be removed to remove any gallium-implanted quartz.The sacrificial layer can be removed, for example, using a broad ionbeam.

[0041] To ensure that defects are removed without damaging thesubstrate, the edges can be verified in situ with imaging software asdescribed in U.S. patent application for “Graphical Automated MachineControl and Metrology” filed Aug. 23, 2002 by Tasker et al.

[0042] In another embodiment, a laser is used to coarsely remove patterncontaining any defect, and a FIB or electron beam is used to recreateentire pattern with improved fidelity. The pattern is recreated bycharged particle beam deposition, or, for example, in a phase shiftmask, by etching. The use of lasers is described, for example, in U.S.Pat. No. RE37,585 to Mourou et al. and U.S. Pat. No. 6,333,485 to Haightet al.

[0043] In other embodiment, one can use a removable passivation ofnon-defective regions of the mask during etch gas chemistries. Such alayer is described in U.S. patent application Ser. No. 10/206,843.

[0044] In accordance with various repair strategies that can be used, awork piece can be processesed using an electron beam or an ion beam. Theeffects of ion implantation can be: 1. avoided by using an electron beamfor some operations; 2. used constructively to provide desired opticalproperties; or 3. eliminated by removal of the implanted layer.Multi-stage operations that use a combination of laser beams, ion beams,and electron beams can speed operations and reduce defects. For example,an ion beam can be used to process a defect and then an electron beamcan be used to remove the effects of the ion beam.

[0045]FIG. 3 shows a typical dual beam system 8 that can be used topractice some of the methods of the present invention. Dual beam system8 includes an evacuated envelope 10 having an upper neck portion 12within which are located a liquid metal ion source 14 and a focusingcolumn 16 including extractor electrodes and an electrostatic opticalsystem. Ion beam 18 passes from source 14 through column 16 and betweenelectrostatic deflection means schematically indicated at 20 towardsample 22, which comprises, for example, a photolithography maskpositioned on movable X-Y stage 24 within lower chamber 26. An ion pump28 is employed for evacuating neck portion 12. The chamber 26 isevacuated with turbomolecular and mechanical pumping system 30 under thecontrol of vacuum controller 32. The vacuum system provides withinchamber 26 a vacuum of between approximately 1×10⁻⁷ Torr and 5×10⁴ Torr.When an etch-assisting or an etch retarding gas is used, the chamberbackground pressure is typically about 1×10⁻⁵ Torr.

[0046] High voltage power supply 34 is connected to liquid metal ionsource 14 as well as to appropriate electrodes in focusing column 16 forforming an approximately 1 keV to 60 keV ion beam 18 and directing thesame downwardly. Deflection controller and amplifier 36, operated inaccordance with a prescribed pattern provided by pattern generator 38,is coupled to deflection plates 20 whereby beam 18 may be controlled totrace out a corresponding pattern on the upper surface of sample 22. Thepattern to be traced is described in detail below. In some systems thedeflection plates are placed before the final lens, as is well known inthe art.

[0047] The source 14 typically provides a metal ion beam of gallium,although other ion sources, such as a multicusp or other plasma ionsource, can be used. The source typically is capable of being focusedinto a sub one-tenth micron wide beam at sample 22 for either modifyingthe surface 22 by ion milling, enhanced etch, material deposition, orfor the purpose of imaging the surface 22. An charged particlemultiplier 40 used for detecting secondary ion or electron emission forimaging is connected to video circuit and amplifier 42, the lattersupplying drive for video monitor 44 also receiving deflection signalsfrom controller 36. The location of charged particle multiplier 40within chamber 26 can vary in different embodiments. For example, apreferred charged particle multiplier 40 can be coaxial with the ionbeam and include a hole for allowing the ion beam to pass. A scanningelectron microscope 41, along with its power supply and controls 45, arepreferably provided with the FIB column. A fluid delivery system 46optionally extends into lower chamber 26 for introducing and directing agaseous vapor toward sample 22.

[0048] A door 60 is opened for inserting sample 22 on stage 24 which maybe heated or cooled, and also for servicing the reservoir 50. The dooris interlocked so that it cannot be opened if the system is undervacuum. The high voltage power supply provides an appropriateacceleration voltage to electrodes in ion beam column 16 for energizingand focusing ion beam 18. When it strikes the work piece, material issputtered, that is physically ejected, from the sample. Dual beamsystems are commercially available, for example, from FEI Company,Hillsboro, Oreg., the assignee of the present application. The inventioncan also be practiced on single or multiple beam systems. It ispreferable to have use charge neutralization when repairing a mask,because the insulating substrate tends to accumulate electrical chargewhich can displace the landing position of the beam on the surface, andconsequently alter the location of the repair. For example, charge canbe neutralized using an electron flood gun or an ion generator, asdescribed in U.S. Prov. Pat. App. No. 60/411,699.

[0049] The inventive system described above includes many novel aspectsand has many practical applications. Many of the novel aspects can beapplied independently of the other novel aspects and are thought to beseparately patentable. Not all aspects of the inventions will beincluded in all embodiments.

[0050] Although the present invention and its advantages have beendescribed in detail, it should be understood that various changes,substitutions and alterations can be made herein without departing fromthe spirit and scope of the invention as defined by the appended claims.Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the disclosure of the present invention, processes,machines, manufacture, compositions of matter, means, methods, or steps,presently existing or later to be developed that perform substantiallythe same function or achieve substantially the same result as thecorresponding embodiments described herein may be utilized according tothe present invention. Accordingly, the appended claims are intended toinclude within their scope such processes, machines, manufacture,compositions of matter, means, methods, or steps.

We claim as follows:
 1. A method for repairing a defect in aphotolithography mask including a transparent substrate and a pattern ofopaque material, the defect being an absence of opaque material on anarea that should be covered by an opaque material, the methodcomprising: scanning a beam of metallic ions over the defect area toimplant metallic atoms into the defect area, the metal atoms reducingthe transparency of the defect area without depositing an opaquematerial to cover the defect area.
 2. The method of claim 1 furthercomprising scanning a beam of metallic ions over a non-defective area ofthe transparent substrate near the defect to implant metallic atoms inthe non-defective area, the implantation of the metallic atoms in thenon-defective area causing the aerial image of the repaired mask to moreclosely resemble the aerial image of a non-defective mask.
 3. The methodof claim 1 further comprising thinning an area of the substrate to alterthe phase of transmitted light.
 4. A method for repairing a defect in aphotolithography mask including a transparent substrate and a pattern ofmaterial, a first area around the defect characterized by a designaerial image, the defect being an absence of material on a second areathat should be covered by a material or the presence of material on thesecond area that should not be covered by the material, the methodcomprising: scanning a beam of ions over a third area to implant atomsinto the third area, the atoms altering the third area and causing anactual repaired aerial image of the first area to approximate the designaerial image more closely than did an actual unrepaired aerial image. 5.The method of claim 4 in which the defect comprises a clear defect in abinary mask and in which scanning a beam of ions over a third area to imatoms into the third area includes scanning a beam of metallic ions overthe third area to implant metallic atoms into the third area to reduceits transparency.
 6. The method of claim 5 in which scanning a beam ofmetallic ions over the third area to implant metallic atoms into thethird area to reduce its transparency includes scanning a beam ofmetallic ions over a defect area and a non-defect area to implantmetallic atoms into the defect area and a non-defect area to reducetransparency.
 7. The method of claim 6 in which scanning a beam ofmetallic ions over a defect area and a non-defect area to implantmetallic atoms into the defect area and a non-defect area to reduce itstransparency includes scanning a beam of metallic ions over a defectarea and a non-defect area to implant metallic atoms into the defectarea and a non-defect area adjacent the defect area to reducetransparency.
 8. The method of claim 4 in which the defect comprises aclear defect in a phase shift mask and in which scanning a beam of ionsover a third area to implant atoms into the third area includes scanninga beam of metallic ions over the third area to reduce its thickness toalter the phase of transmitted light and to implant metallic atoms intothe third area to reduce its transparency.
 9. A method for repairing adefect in a photolithography mask, comprising: locating a defect on amask; characterizing the defect; determining an intended aerial imagecorresponding to an area of the mask that includes the defect;determining an alternate structure that will provide an aerial imagesimilar to the intended aerial image; and effecting the alternatestructure on the mask.
 10. The method of claim 9 in which determining analternate structure that will provide an aerial image similar to theintended aerial image includes determining an alternate structure thatincludes an area of metallic atoms implanted by an ion beam.
 11. Themethod of claim 10 in which the area of metallic atoms implanted by anion beam includes an area of an opaque defect.
 12. The method of claim11 in which the area of metallic atoms implanted by an ion beam furtherincludes a non-defective area.
 13. A method for repairing aphotolithography mask including a pattern on a substrate, the maskhaving a defect such that the actual pattern on the mask is differentfrom an intended design pattern, comprising: using a laser to remove anarea of the pattern including the defect; using one or more chargedparticle beams to recreate in the area a pattern that providesapproximately the aerial image as the intended design pattern in thearea.
 14. The method of claim 13 in which using one or more chargedparticle beams to recreate in the area a pattern that providesapproximately the aerial image as the intended design pattern in thearea includes using an ion beam to implant atoms to alter thetransparency of a portion of the mask.
 15. The method of claim 13 inwhich using one or more charged particle beams to recreate in the area apattern that provides approximately the aerial image as the intendeddesign pattern in the area includes using an ion beam to deposit ions toalter the transparency of a portion of the mask includes using a chargedparticle beam to etch a portion of the mask to alter the phase oftransmitted light.
 16. A method for repairing a defect in aphotolithography mask, comprising measuring a defect in three dimensionsby forming at least two images using charged particle beams at differentincident angles; and using the three dimensional information to programa charged particle beam system to etch the defect.
 17. A method forrepairing a defect in a photolithography mask, comprising: providing asacrificial layer of quartz on the mask substrate; directing an ion beamtoward the mask to repair a defect by depositing material or removingexcess material, at least some of the ions implanting into thesacrificial layer as implanted atoms and reducing the transparency ofthe mask substrate; and removing the sacrificial layer, thereby removingthe implanted atoms and increasing the transparency of the masksubstrate.
 18. The method of claim 17 in which removing the sacrificiallayer includes directing a broad ion beam at the mask to etch away thesacrificial layer.
 19. A method for repairing a clear defect in a phaseshift photolithography mask, comprising: supplying a quartz-producingprecursor gas to the defect area; and directing an electron beam towarda defect area, the quartz-producing precursor gas decomposing in thepresence of the electron to deposit quartz onto the defect area.
 20. Themethod of claim 19 in which supplying a quartz-producing precursor gasto the defect area includes supplying TEOS or TMCTS to the defect area.21. The method of claim 19 in which directing a quartz-producingprecursor gas toward the defect area further comprises supplying anoxygen containing material to the defect area.
 22. The method of claim21 in which supplying an oxygen containing material includes supplyingwater, oxygen or hydrogen peroxide.
 23. A method for repairing a opaquedefect in a photolithography mask, comprising: directing an ion beamtoward an area of the mask including the defect to remove material, theion beam incidentally implanting atoms into the mask, thereby reducingits transparency; and directing an electron beam toward the area of themask to remove a layer of the mask containing the implanted atoms and toincrease the transparency of the area.
 24. The method of claim 21 inwhich directing an electron beam toward the area of the mask includesdirecting an etchant gas toward the area of the mask.
 25. The method ofclaim 24 in which the etchant gas comprises xenon difluoride.